Marion left home at 11.55 a.m. and drove towards the seaside resort. 2 hours later, her cousin left their home and drove towards the same seaside resort at 85 km/h. When the cousin reached the seaside resort at 4.55 p.m., Marion had another 5 km to travel. What was Marion’s average speed? Express your answer in mixed number.
Time that the Marion's cousin started driving = 1.55 p.m.
Duration that Marion's cousin drove from 1.55 p.m. to 4.55 p.m. = 3 h

Distance that Marion's cousin travelled
= 3 x 85
= 255 km

Distance that Marion travelled by the time her cousin reached the city
= 255 - 5
= 250 km

Time that Marion took to travel 250 km = 5 h

Marion's average speed
= 250 ÷ 5
= 50 km/h

Answer(s): 50 km/h